Many reasons arise which necessitate that the life of an animal must be terminated with minimal pain and distress. The reasons for euthanasia may include the diagnosis of an incurable disease such as cancer, painful medical conditions, broken limbs, exposure to the rabies virus, deterioration and impairment due to old age, and/or dissection and analysis of animals used in laboratory experimentation. There are a number of methods for performing euthanasia on various different animals, and many organizations promulgate standards for these procedures, including those of the American Veterinary Medical Association—The AVMA Guidelines on Euthanasia. These methods may generally be categorized as Physical Methods (e.g., penetrating captive bolt, shotgun, . . . ), Non-inhalant Pharmaceutical Agents (Barbiturates, Potassium Chloride, . . . ), and Inhalant Agents (e.g., Carbon Dioxide, Nitrogen, Argon . . . ). In many instances it is desirable to terminate the animals with inhalant agents. Furthermore, it is advantageous in many instances to terminate multiple large-sized animals at the same time, preferably within their own cages. Although there have been a number of devices heretofore developed to assist operators in euthanizing animals, they fail to fully accommodate performance of the process in strict accordance with many guidelines necessary to safely complete the procedure—both for the safety of the operator, and for the safe and humane treatment of the animals to be terminated. The apparatus of the present invention overcomes many of the disadvantages of the prior art, which will become apparent in the subsequent discussion.